The present invention relates to an electro-optical device, and in particular to an electro-optical device having a color filter layer.
Various methods for forming a transparent electrode on a color filter have been proposed hitherto as disclosed in Japanese Patent Unexamined Publication No. 61-233720, Japanese Patent Unexamined Publication No. 61-260224, Japanese Patent Unexamined Publication No. 61-198131 or Japanese Patent Unexamined Publication No. 62-153826.
However, in the aforementioned prior art, color filters and protective layers are formed from organic resins for easy formation of fine patterns. Because the heat resistance of these organic resins is low (approximately 220.degree. C. to 230.degree. C. at highest), when the transparent electrode is formed either directly on the color filter or on the protective layer, the processing temperatures cannot be raised at the time of coating and this leads to an undesirably weak film quality for the transparent electrode film material. This in turn leads to the undesirable property of low surface hardness, and hence an unsatisfactory physical strength. Also an electric corrosion reaction is induced when an electric field is applied in an environment where an electrolyte such as water exists. These problems manifest themselves as low reliability for the electro-optic device. Because of this, a method for pigmenting a color filter formed through a dyeing process hitherto is employed for enhancing the heat resistance of the color filter itself, however, the problem is inherent in the heat resistance of the holding resin itself, and hence an improvement is not realizable.
An attempt to enhance the heat resistance of the resin has been unsuccessful because problems, such as short wavelength light being absorbed act to turn the resin yellow. Also the resistance of the electro-optic device to alkali is reduced when heat resistance enhanced resins are used.
Alternatively a method for forming the color filter by sublimiting a substance with high heat resistance such as pigment into a porous inorganic layer has been proposed. However, there yet remain problems with pattern precision and color purity which are unsolved.
What is desirable is to provide an electro-optic device having a transparent electrode on a color filter directly, or through a single or plural organic or inorganic layer, which has improved chemical durability, particularly a high resistance to electric corrosion reactions and is generally high in reliability.